Force effects on anatomical structures in transoral surgery − videolaryngoscopic prototype vs. conventional direct microlaryngoscopy

Abstract

Direct microlaryngoscopy is a frequently performed procedure in otorhinolaryngology, whereby considerable force is exerted on the patients’ teeth, as well as oropharyngeal and laryngeal structures. Especially in cases of a challenging exposure of the anterior commissure, the cervical spine needs to be brought into a hyperextended position, which is not possible in every patient. Therefore, the conflict between the straight rigid microlaryngoscope and the curvature of the oropharyngeal corridor frequently results in tissue trauma with the consequence of teeth fracture, hematoma or nerve injury. We have developed the s-MAC system, a hyper-angulated video laryngoscope with flexible instruments for transoral laryngeal surgery, which so far shows high feasibility in preclinical studies. Due to its curved shape it may exert less force on teeth and supraglottis as conventional direct microlaryngoscopy. We quantified the effects of these two surgical systems using flexible pressure sensors in two different scenarios: a mobile, hyperextended and an immobile cervical spine of the dummy, to simulate a challenging airway. We could demonstrate a 21% (40% with immobilized cervical spine) reduction of the average peak force acting on the maxillary incisors and a 55% (65% with immobilized cervical spine) reduction of the average intraoperative force on the supraglottis. The developed prototype applied therefore significantly less force on upper front teeth and supraglottis as compared to conventional direct microlaryngoscopy – especially in the case of an immobilized cervical spine.

Keywords

• force
• larynx
• surgery
• tlm
• video laryngoscope